Process for producing optically active 2-[6-(hydroxymethyl)-1,3-dioxan-4yl]acetic acid derivatives

ABSTRACT

This invention provides a process for producing optically active 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivatives, which are of value as intermediates of drugs, from inexpensive starting materials without using any special equipment such as that required for super-low temperature reactions.  
     A process for producing optically active 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivatives which comprises  
     reacting an acetic acid derivative at a temperature of not less than −30° C. with an enolate prepared by permitting either a base or a metal having a valency of 0 to act on the derivative to produce a hydroxyoxohexanoic acid derivative,  
     reducing this compound with the aid of a strain of microorganism to provide a halomethyldioxanylacetic acid derivative,  
     treating this compound with an acetalizing agent in the presence of an acid catalyst to provide a halomethyl-dioxanylacetic acid derivative,  
     reacted with an acyloxylating agent to provide a acyloxymethyldioxanylacetic acid derivative, and  
     subjecting this compound to solvolysis in the presence of a base.

TECHNICAL FIELD

[0001] The present invention relates to a process for producingoptically active 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acidderivatives which are of value as intermediates of drugs, particularlyintermediates of HMG-CoA reductase inhibitors.

BACKGROUND ART

[0002] For the production of a2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivative, thefollowing processes are known.

[0003] (1) A process starting with 3-hydroxy-γ-butyrolactone tosynthesize a 3,5,6-trihydroxyhexanoic acid ester derivative via a3,5-dihydroxyhexanoic acid ester derivative (Japanese Kokai PublicationHei-4-173767).

[0004] (2) A process starting with 3,4-dihydroxybutyronitrile acetonideto synthesize a 3,5,6-trihydroxyhexanoic acid ester derivative via a3,5-dihydroxyhexanoic acid ester derivative (Japanese Kokai PublicationHei-2-262537).

[0005] (3) A process starting with a 4-chloroacetoacetic acid ester tosynthesize a 3,5,6-trihydroxyhexanoic acid ester derivative viaconversion to a benzyloxy derivative, reduction and chain extension(Japanese Kokai Publication Hei-6-65226).

[0006] (4) A process starting with a 4-chloro-3-hydroxybutyric acidester to synthesize a 3,5,6-trihydroxyhexanoic acid ester derivativethrough chain extension, reduction, etc. (U.S. Pat. No. 5,278,313).

[0007] (5) A process starting with malic acid to synthesize a 3,5,6-trihydroxyhexanoic acid ester via a 2, 4-dihydroxyadipic acidderivative (Japanese Kokai Publication Hei-4-69355).

[0008] However, those processes involve reactions at a super-lowtemperature in the neighborhood of −80° C. (1, 2, 4, 5) or ahydrogenation reaction at a high pressure of 100 kg/cm² (3), thusrequiring the use of special reaction equipment. Moreover, the processesinvolve the use of costly reagents in some stage or other and,therefore, none of them is an efficient process for commercial-scaleproduction.

[0009] The prior art process (4), for instance, comprises reacting a4-chloro-3-hydroxybutyric acid ester with an enolate of tert-butylacetate using costly lithium hexamethyl disylazide at a super-lowtemperature of −78° C. in the first step and performing astereoselective reduction using costly diethylmethoxyborane and sodiumborohydride, again at a super-low temperature of −78° C., in the secondstep. This process further involves an acetoxylation reaction withcostly tetra-n-butylammonium acetate in the costly solvent1-methyl-2-pyrrolidinone.

SUMMARY OF THE INVENTION

[0010] The present invention, developed in the above state of the art,has for its object to provide an expedient process for producing anoptically active 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acidderivative of the following general formula (I) from inexpensivestarting materials without using any special equipment such as thatrequired for super-low temperature reactions.

[0011] wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to12 carbon atoms, R⁴ and R⁵ each independently represents hydrogen, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, and R⁴ and R⁵ may beconjoined each other to form a ring.

[0012] As the result of intensive investigations made in light of theabove state of the art, the inventors of the present invention havedeveloped an expedient process for producing an optically active2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivative of thefollowing general formula (I):

[0013] wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to12 carbon atoms, R⁴ and R⁵ each independently represents hydrogen, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, and R⁴ and R⁵may beconjoined each other to form a ring, from inexpensive, readily availablestarting materials without employing any extraordinary equipment such asthat required for low-temperature reactions.

[0014] The present invention, thus, is concerned with a process forproducing said optically active2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivative (I):

[0015] wherein R¹, R⁴ and R⁵ are respectively as defined below, whichcomprises

[0016] (1) a step comprising reacting an enolate prepared by permittingeither a base or a metal having a valency of 0 to act on an acetic esterderivative of the following general formula (II):

X²CH₂CO₂R¹  (II)

[0017] wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to12 carbon atoms, X² represents hydrogen or a halogen atom,

[0018] with a compound of the following general formula (III):

[0019] wherein R² represents an alkyl group of 1 to 12 carbon atoms, anaryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, X¹ represents a halogen atom

[0020] at a temperature of not less than −30° C. to give a compound ofthe following general formula (IV):

[0021] wherein R¹ and X¹ are respectively as defined above,

[0022] (2) a step comprising reducing this compound with the aid of astrain of microorganism to give a compound of the following generalformula (V):

[0023] wherein R¹ and X¹ are respectively as defined above,

[0024] (3) a step comprising treating this compound with an acetalizingagent in the presence of an acid catalyst to give a compound of thefollowing general formula (VI):

[0025] wherein R¹ and X¹ are respectively as defined above, R⁴ and R⁵each independently represents hydrogen, an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to12 carbon atoms, and R⁴ and R⁵ may be conjoined each other to form aring,

[0026] (4) a step comprising acyloxylating this compound with anacyloxylating agent to give a compound of the following general formula(VII):

[0027] wherein R¹, R⁴ and R⁵ are respectively as defined above, R³represents hydrogen, an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and

[0028] (5) a step comprising subjecting this compound to solvolysis inthe presence of a base.

DISCLOSURE OF THE INVENTION

[0029] The present invention is now described in detail.

[0030] The present invention is constituted by 5non-super-low-temperature reaction steps (1) to (5) as illustrated inthe following reaction scheme.

[0031] The following is a step-by-step description of the presentinvention.

[0032] Step (1)

[0033] In this step, an enolate prepared by permitting either a base ora metal having a valency of 0 to act upon an acetic ester derivative ofthe following general formula (II):

X²CH₂CO₂R¹  (II)

[0034] is reacted with a (3S) configured hydroxybutyric acid esterderivative of the following general formula (III):

[0035] at a temperature of not less than −30° C. to produce a(5S)-configured hydroxyoxohexanoic acid derivative of the followinggeneral formula (IV):

[0036] Generally when a reaction involving the enolate of an aceticester or the like is conducted under non-super-low-temperaturecondition, e.g. at not less than −30° C., the self-condensation of theenolate proceeds predominantly to considerably detract from theconversion rate of the objective reaction. However, by the followingprocedure developed by the present inventors, the self-condensation ofthe acetic ester enolate can be minimized so that the objective reactioncan be conducted with good yield.

[0037] In the hydroxybutyric acid derivative to be used in step (1),namely a compound of the following general formula (III):

[0038] the configuration of the 3-position is (S) and R² is, forexample, an alkyl group of 1 to 12 carbon atoms, an aryl group of 6 to12 carbon atoms or an aralkyl group of 7 to 12 carbon atoms, thus as aspecific example, there can be mentioned methyl, ethyl, i-propyl,tert-butyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl andp-nitrobenzyl, among others. The preferred is methyl or ethyl, withethyl being the more preferred.

[0039] X¹ represents a halogen atom, e.g. chloro, bromo and iodo, and ispreferably chloro or bromo. The more preferred is chloro.

[0040] Optically active hydroxybutyric acid derivatives having the (3S)configuration can be produced on a high production scale by the knowntechnology (inter alia, Japanese Patent Publication No.1723728).

[0041] Referring to the acetic ester derivative for use in step (1), R¹represents hydrogen, an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, as a specific example, there can be mentioned hydrogen, methyl,ethyl, i-propyl, tert-butyl, n-octyl, phenyl, naphthyl, p-methoxyphenyland p-nitrobenzyl, among others. The preferred is tert-butyl.

[0042] X² represents hydrogen or halogen, as a specific example, therecan be mentioned hydrogen, chloro, bromo and iodo. The preferred speciesare hydrogen and bromo.

[0043] The amount of use of the acetic ester derivative is 1 to 10 molarequivalents, preferably 1 to 5 molar equivalents, relative to thehydroxybutyric acid.

[0044] In step (1), an enolate is first prepared by permitting either abase or a metal having a valency of 0 to act upon the acetic esterderivative.

[0045] Generally, a base is used in the preparation of its enolate whenX² of the acetic ester is hydrogen, while a metal having a valency of 0is used when X² is a halogen atom.

[0046] As the base which can be used in the preparation of the enolate,there can be mentioned lithium amide compounds such as lithium amide,lithium diisopropylamide, lithium dicyclohexylamide, lithium hexamethyldisylazide, etc.; magnesium amides such as magnesium chloridediisopropylamide, magnesium bromide diisopropylamide, magnesium iodidediisopropylamide, magnesium chloride dicyclohexylamide, etc.; sodiumamides such as sodium amide, sodium diisopropylamide, etc., potassiumamides such as potassium amide, potassium diisopropylamide, etc.;alkyllithium compounds such as methyllithium, n-butyllithium,t-butyllithium, etc.; Grignard reagents such as methylmagnesium bromide,i-propylmagnesium chloride, t-butylmagnesium chloride, etc.; metalalkoxides such as sodium methoxide, magnesium ethoxide, potassiumtert-buthoxide, etc.; and metal hydrides such as lithium hydride, sodiumhydride, potassium hydride, calcium hydride, etc.; among others.

[0047] The base is preferably a metal hydride, a magnesium amide, alithium amide, or a Grignard reagent.

[0048] Those bases are used each alone or in combination. For example, alithium amide or a metal hydride is more effective when used incombination with a Grignard reagent or a magnesium-containing base suchas a magnesium amide.

[0049] The magnesium-containing base can be used in the combination ofthe base with a magnesium compound such as magnesium chloride, magnesiumbromide or the like.

[0050] The magnesium amide can be represented by the following generalformula (VIII):

[0051] In the above formula, R⁶ and R⁷ each independently represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms, an aralkyl group of 7 to 12 carbon atoms or a silyl group, as aspecific example, there can be mentioned methyl, ethyl, i-propyl,tert-butyl, cyclohexyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl,p-nitrobenzyl, trimethylsilyl, triethylsilyl, and phenyldimethylsilyl,among others. The preferred species is isopropyl. X³ represents ahalogen atom which is preferably chloro, bromo or iodo. The morepreferred is chloro.

[0052] The magnesium amide can be prepared by the well-known methodusing a readily available secondary amide and a Grignard reagent (e.g.Japanese Kokai Publication Hei-8-523420). As an alternative, it can beprepared using a lithium amide and a magnesium halide in accordance witha known process (e.g. J. Org. Chem. 1991, 56, 5978-5980).

[0053] The lithium amide can be represented by the following generalformula (X):

[0054] In the above formula, R⁹ and R¹⁰ each independently represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms, an aralkyl group of 7 to 12 carbon atoms, or a silyl group, as aspecific example, there can be mentioned methyl, ethyl, i-propyl,tert-butyl, cyclohexyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl,p-nitrobenzyl, trimethylsilyl, triethylsilyl, and phenyldimethylsilyl.The preferred example is isopropyl.

[0055] The Grignard reagent is represented by the following generalformula (IX):

X⁴—Mg—R⁸  (IX)

[0056] In the formula, R⁸ represents an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to12 carbon atoms, as a specific example, there can be mentioned methyl,ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, n-octyl, phenyl,naphthyl, p-methoxyphenyl and p-nitrobenzyl. The preferred is methyl,ethyl, i-propyl, n-butyl or tert-butyl. The still more preferred istert-butyl. X⁴ represents a halogen atom, which is preferably chloro,bromo or iodo. The more preferred is chloro.

[0057] The amount of use of the base in step (1) is 1 to 10 molarequivalents, preferably 2 to 6 molar equivalents, relative to thehydroxybutyric acid derivative.

[0058] The metal having a valency of 0 which can be used in thepreparation of said enolate in step (1) includes zinc, magnesium, tin,etc. and is preferably zinc or magnesium.

[0059] The amount of use of the metal having a valency of 0 in step (1)is 1 to 20 molar equivalents, preferably 2 to 8 molar equivalents,relative to the hydroxybutyric acid derivative.

[0060] The solvent which can be used in step (1) may for example be anaprotic organic solvent. The organic solvent mentioned above includeshydrocarbon series solvents, such as benzene, toluene, n-hexane,cyclohexane, etc.; ether series solvents such as diethyl ether,tetrahydrofuran, 1,4-dioxane, methyl t-butyl ether, dimethoxyethane,ethylene glycol dimethyl ether, etc.; halogen-containing solvents suchas methylene chloride, chloroform, 1,1,1-trichloroethane, etc.; andaprotic polar solvents such as dimethylformamide, N-methylpyrrolidone,hexamethylphosphorotriamide, etc., among others. These solvents can beused each alone or in a combination of two or more species. Thepreferred, among the above solvents, are hydrocarbon series solventssuch as benzene, toluene, n-hexane, cyclohexane, etc. and ether seriessolvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane, methylt-butyl ether, dimethoxyethane, diethylene glycol dimethyl ether, etc.The more preferred are polyether series solvents such as dimethoxyethaneand diethylene glycol dimethyl ether. Polyether series solvents may eachbe used as a sole solvent or an additive to a different reactionsolvent. The addition amount in the latter case may be 1 to 10 molarequivalents relative to the hydroxybutyric acid derivative. The solventwhich is particularly preferred is dimethoxyethane.

[0061] The reaction temperature for step (1) is preferably −30° C.to-100° C., more preferably −10° C. to 60° C.

[0062] In step (1), while the order of addition of reactants may bearbitrary, the hydroxybutyric acid derivative may be treated with thebase beforehand. Preferably, it is treated with the base and themagnesium compound beforehand.

[0063] As the preferred base, there can be mentioned metal hydrides andlithium amides.

[0064] As the preferred magnesium compound, there can be mentionedmagnesium chloride and magnesium bromide.

[0065] The base and the magnesium compound need not be independentcompounds but a magnesium-containing base can be employed.

[0066] As the preferred magnesium-containing base, there can bementioned Grignard reagents such as methylmagnesium bromide,i-propylmagnesium chloride, tert-butylmagnesium chloride, etc. andmagnesium amides such as magnesium chloride diisopropylamide, magnesiumbromide diisopropylamide, magnesium iodide diisopropylamide, magnesiumchloride dicyclohexylamide and so forth.

[0067] At the pretreatment of the hydroxybutyric acid derivative, apretreatment of a mixed solution of the hydroxybutyric acid derivativeand acetic ester derivative is allowed. After this pretreatment, thereaction can be advantageously carried out by adding the base, such as alithium amide, e.g. lithium amide, lithium diisopropylamide, lithiumdicyclohexylamide or lithium hexamethyldisilazide, or a magnesium amide,or a solution of the base dropwise.

[0068] The proportion of the base for use in the pretreatment is 0.01 to3 molar equivalents, preferably 0.5 to 1.5 molar equivalents, relativeto the hydroxybutyric acid derivative.

[0069] The proportion of the magnesium compound for use in thepretreatment is 0.1 to 10 molar equivalents, preferably 0.5 to 1.5 molarequivalents, relative to the hydroxybutyric acid derivative.

[0070] The proportion of the magnesium-containing base for use in thepretreatment is 0.01 to 3 molar equivalents, preferably 0.5 to 1.5 molarequivalents, relative to the hydroxybutyric acid derivative.

[0071] The proportion of the base to be reacted after the pretreatmentis 1 to 20 molar equivalents, preferably 2 to 8 molar equivalents,relative to the hydroxybutyric acid.

[0072] Thus, this step (1) can be advantageously carried out by treatingthe hydroxybutyric acid derivative with a base and a magnesiumderivative in the first place and then causing a base to act on the samein the presence of an acetic ester derivative.

[0073] As an alternative, the hydroxybutyric acid derivative may bepretreated with a Grignard reagent and, then, reacted with an enolateprepared by permitting a metal having a valency of 0 to act on an aceticester derivative.

[0074] After completion of the reaction in step (1), the reactionproduct can recovered from the reaction mixture by the routineafter-treatment. For example, the reaction mixture after completion ofreaction is mixed with the common inorganic or organic acid, e.g.hydrochloric acid, sulfuric acid, nitric acid, acetic acid or citricacid, and the mixture is then extracted with the common extractionsolvent, e.g. ethyl acetate, diethyl ether, methylene chloride, tolueneor hexane. From the extract obtained, the reaction solvent andextraction solvent are distilled off by heating under reduced pressureetc. isolate the objective compound. The product thus obtained is asubstantially pure compound but may be further purified by aconventional technique such as recrystallization, fractionaldistillation, column chromatography or the like.

[0075] Step (2)

[0076] In this step, the hydroxyoxohexanoic acid derivative obtained instep (1), namely a (5S)-configured hydroxyoxohexanoic derivative of thefollowing general formula (IV);

[0077] is subjected to the reduction with a strain of microrganism toprovide a (3R,5S)-configured dihydroxyhexanoic acid derivative of thefollowing general formula (V).

[0078] In the case of the stereoselective reduction of the carbonylgroup of such a hydroxyoxohexanoic acid derivative, the technique isgenerally adapted in which the reduction reaction is carried out with ahydride series reducing agent such as sodium borohydride in the presenceof an alkylborane at a super-low temperature (e.g. U.S. Pat. No.5,278,313).

[0079] The inventors of the present invention developed amicrobiological reduction technology by which a hydroxyoxohexanoic acidderivative can be reduced at low cost with good stereoselectivity at anon-super-low temperature.

[0080] The microorganism capable of reducing a hydroxyoxohexanoic acidderivative to a dihydroxyhexanoic acid derivative, which is for use inthis step (2), can be selected by the method described below. Forexample, a 500-mL Sakaguchi flask is charged with 50 mL of Medium A (pH6.5) comprising 5% of glucose, 0.5% of peptone, 0.2% of potassiumdihydrogen phosphate, 0.1% of dipotassium hydrogen phosphate, 0.02% ofmagnesium sulfate and 0.1% of yeast extract. After sterilization, theflask is inoculated with a strain of microorganism and incubated undershaking at 30° C. for 2 to 3 days. The cells are harvested bycentrifugation and suspended in 25 mL of a phosphate buffer solutioncontaining 0.1 to 0.5% of tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate and 5% of glucose, and theresulting suspension is shaken in a 500-mL Sakaguchi flask at 30° C. for2 to 3 days. After completion of the conversion reaction, the reactionmixture is extracted with one volume of ethyl acetate and the extract isanalyzed for tert-butyl 6-chloro-3,5-dihydroxyhexanoate by highperformance liquid chromatography [column: Nakalai Tesque's Cosmocil5CN-R (4.6 mm×250 mm), eluent: 1 mM phosphoricacid/water:acetonitrile=5:1, flow rate: 0.7 mL/min., detection at 210nm, column temperature 30° C., elution time [tert-butyl(3S,5S)-6-chloro-3,5-dihydroxyhexanoate: 12.5 min.; terty-butyl(3R,5S)-6-chloro-3,5-dihydroxyhexanoate: 13.5 min., tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate: 17 min.].

[0081] The bacterial strain capable of reducing a hydroxyoxohexanoicacid derivative to a dihydroxyhexanoic acid derivative, which can beused in step (2), can be selected by the method described below. Forexample, a large-sized test tube is charged with 7 mL of Medium B (pH7.0) comprising 1% of meat extract, 1% of polypeptone, 0.5% of yeastextract and 0.5% of glucose. After sterilization, the test tube isinoculated with a test strain and shake culture is carried out at 30° C.for ½ day. The cells are harvested by centrifugation and suspended in0.5 mL of a phosphate buffer solution containing 0.1 to 0.5% oftert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate and glucose. Thissuspension is shaken in a 10-mL stoppered test tube at 30° C. for 1˜2days. After completion of the conversion reaction, the reaction mixtureis extracted by adding one volume of ethyl acetate and the extract isanalyzed for tert-butyl 6-chloro-3,5-dihydroxyhexanoate by highperformance liquid chromatography.

[0082] As the strains of microorganism which can be used in the practiceof this invention, there can be mentioned those belonging to the generaHormoascus, Candida, Cryptococcus, Debaryomyces, Geotrichum, Kuraishia,Hansenulla, Kluyveromyces, Pichia, Yamadazyma, Rhodotorula,Saccharomyces, Schizoblastosporon, and Zyaosaccharomyces. Moreparticularly, there can be used such strains as Hormoascus platypodisIFO1471, Candida catenulata IFO0745, Candida diversa IFO1019, Candidafructus IFO1581, Candida glaebosa IFO1353, Candida guilliermondiiIFO0454, Cryptococcus humicola IFO0760, Candida intermedia IFO0761,Candida magnoliae IFO0705, Candida musae IFO1582, Candida pintolopesiivar. pintolopenii IFO0729, Candida pinus IFO0741, Candida sake IFO0435,Candida sonorensis IFO10027, Candida tropicalis IFO1401, Cryptococcuslaurentii IFO0609, Cryptococcus terreus IFO0727, Debaryomyces hanseniivar. fabryi IFO0058, Geotrichum eriense ATCC22311, Kuraishia capsulataIFO0721, Kluyveromyces marxianus IFO0288, Pichia bovis IFO1886,Yamadazyma haplophila IFO0947, Pichia membranaefaciens IFO0458,Rhodotorula glutinis IFO1099, Saccharomyces cerevisiae IFO0718,Schizoblastosporon kobayasii IFO1644, Candida claussenii IFO00759,Debaryomyces robertsii IFO1277 and Zygosaccharomyces rouxii IFO0493,among others. Those microorganisms can be generally obtained, free ofcost or at cost, from culture collections which are readily accessible.Or they may be isolated from the natural kingdom. Furthermore, thosemicroorganisms may be subjected to mutation to derive strains having themore favorable characters for the present reaction.

[0083] While the microorganisms which can be used in the presentinvention include bacteria of the genera Brevibacterium,Corynebacterium, and Rhodococcus, specifically the following bacterialstrains, among others, can be used. Brevibacterium stationis IFO12144,Corynebacterium ammoniagenes IFO12072, Corynebacterium flavescensIFO14136, Corynebacterium alutamicum ATCC13287, Rhodococcus erythropolisIAM1474. Those microorganisms can be generally obtained, free of cost orat cost, from culture collections which are readily accessible. Or theymay be isolated from the natural kingdom. Furthermore, these bacteriamay be subjected to mutation to derive strains having the more favorablecharacters for the present reaction.

[0084] In cultivation of the above-mentioned strains of microorganisms,any nutrient source is utilized by microorganisms in general. Forexample, as sources of carbon, there can be used various sugars such asglucose, sucrose, maltose, etc.; organic acids such as lactic acid,acetic acid, citric acid, propionic acid, etc.; alcohols such asethanol, glycerol, etc.; hydrocarbons such as paraffin etc.; oils suchas soybean oil, rapeseed oil, etc.; and various mixtures thereof. Assources of nitrogen there can be used a variety of nitrogenoussubstances such as ammonium sulfate, ammonium phosphate, urea, yeastextract, meat extract, peptone, and corn steep liquor, among others. Theculture medium may be further supplemented with inorganic salts,vitamins and other nutrients.

[0085] Culture of microorganisms can be generally carried out underroutine conditions, for example within the range of pH 4.0 to 9.5 at atemperature 20 to 45° C. aerobically for 10 to 96 hours. In permitting astrain of microorganism to act on the hydroxyoxohexanoic acidderivative, generally the culture broth obtained can be submitted as itis to the reaction but a concentrate of the broth can also be employed.Moreover, in case some component in the culture broth is suspected toadversely affect the reaction, the cells separated by, for example,centrifugation of the broth can be used as such or after furtherprocessing.

[0086] The product available after said further processing is notparticularly restricted but there can be mentioned dried cells which canbe obtained by dehydration with acetone or diphosphorous pentoxide ordrying over a desiccant or with the draft air of a fan, the product ofsurfactant treatment, the product of bacteriolytic enzyme treatment,immobilized cells, and a cell-free extract obtainable from disruptedcells. A still further alternative comprises purifying the enzymecatalyzing a chiral reduction reaction from the culture broth and employthe purified enzyme.

[0087] In conducting the reduction reaction, the substratehydroxyoxohexanoic acid derivative may be added en bloc at initiation ofthe reaction or in several installments as the reaction proceeds.

[0088] The reaction temperature is generally 10 to 60° C., preferably 20to 40° C., and the reaction pH is 2.5 to 9, preferably 5 to 9.

[0089] The concentration of the microbes in the reaction system can bejudiciously selected according to the ability of the strain to reducethe substrate. The substrate concentration of the reaction system ispreferably 0.01 to 50% (w/v), more preferably 0.1 to 30%.

[0090] The reaction is generally carried out under shaking or underaeration and stirring. The reaction time setting is selected accordingto the substrate concentration, the concentration of the microbes, andother reaction conditions. It is generally preferable to set variousconditions so that the reaction will go to completion in 2 to 168 hours.

[0091] For the purpose of accelerating the reduction reaction, an energysource, such as glucose or ethanol, can be added at the amount of 1 to30% to the reaction mixture with advantage. Moreover, the reaction canbe accelerated by adding a coenzyme, such as reduced nicotinamideadenine dinucleotide (NADH) or reduced nicotinamide adenine dinucleotidephosphate (NADPH), which is known to be generally necessary forbiological reduction systems in general. Thus, such a coenzyme may bedirectly added to the reaction mixture or, alternatively, a reactionsystem giving rise to NADH or NADPH and an oxidized-form coenzyme may beadded together to the reaction mixture. For example, a reaction systemin which formate dehydrogenase reduces NAD to NADH when carbon dioxideand water are produced from formic acid or a reaction system in whichglucose dehydrogenase reduces NAD or NADP to NADH or NADPH whengluconolactone is produced from glucose can be utilized. It is alsouseful to add a surfactant such as Triton (Nakalai-Tesque), Span (KantoChemical) or Tween (Nakalai-Tesque) to the reaction system. Furthermore,for the purpose of obviating the inhibition of the reaction by thesubstrate and/or the reduction product alcohol, a water-insolubleorganic solvent such as ethyl acetate, butyl acetate, isopropyl ether,toluene or the like can be added to the reaction system. Moreover, forenhancing the solubility of the substrate, a water-soluble organicsolvent such as methanol, ethanol, acetone, tetrahydrofuran or dimethylsulfoxide can be added.

[0092] The reduction product dihydroxyhexanoic acid derivative can beharvested directly from the culture broth or isolated from harvestedcells by extraction with a solvent such as ethyl acetate, toluene or thelike, followed by removal of the solvent. The product may be furtherpurified by recrystallization, silica gel column chromatography or thelike procedure to provide the dihydroxyhexanoic acid derivative ofhigher purity.

[0093] Step (3)

[0094] In this step, the (3R, 5S)-configured dihydroxyhexanoic acidderivative obtained in step (2), namely the compound of the followinggeneral formula (V):

[0095] , is subjected to the known acetalization reaction, for exampletreatment with an acetalizing agent in the presence of an acid catalyst,to provide a (4R,6S)-configured halomethyldioxanylacetic acid derivativeof the following general formula (VI).

[0096] As the acetalizing agent which can be used in this step (3),there can be mentioned ketones, aldehydes, alkoxyalkanes, andalkoxyalkenes. As specific examples of said ketones, aldehydes,alkoxyalkanes and alkoxyalkenes, there can be mentioned acetone,cyclohexanone, formaldehyde, benzaldehyde, dimethoxymethane,2,2-dimethoxypropane, 2-methoxypropene, 1,1-dimethoxycyclohexane, and soforth. The preferred acetalizing agents are acetone, 2-methoxypropeneand 2,2-dimethoxypropane.

[0097] The amount of the acetalizing agent to be used in step (3) ispreferably 1 to 10 molar equivalents, more preferably 1 to 5 molarequivalents, relative to the dihydroxyhexanoic acid derivative. Forexpediting the reaction, the acetalizing agent can be utilized as thereaction solvent.

[0098] The acid catalyst which can be used in step (3) is a Lewis acidor a Brønstead acid. As the Lewis acid and Brønstead acid mentionedabove, there can be mentioned such Lewis acids as aluminum trichloride,boron trifluoride, zinc dichloride, tin tetrachloride, etc.; carboxylicacids such as oxalic acid, formic acid, acetic acid, benzoic acid,trifluoroacetic acid, etc.; sulfonic acids such as methanesulfonic acid,p-toluenesulfonic acid, camphorsulfonic acid, pyridiniump-toluenesulfonate, etc.; and inorganic acids such as hydrochloric acid,sulfuric acid, nitric acid and boric acid. The preferred arep-toluenesulfonic acid, camphorsulfonic acid and pyridiniump-toluenesulfonate.

[0099] The amount of the acid catalyst to be used in step (3) ispreferably 0.001 to 0.5 molar equivalent, more preferably 0.005 to 0.1molar equivalent, relative to the dihydroxyhexanoic acid derivative.

[0100] The reaction in step (3) can be carried out in the absence of asolvent but various organic solvents can be used as a reaction solvent.As such organic solvents, there can be mentioned hydrocarbon seriessolvents such as benzene, toluene, cyclohexane, etc.; ether seriessolvents such as diethyl ether, tetrahydrofuran, 1,4-dioxane, methylt-butyl ether, dimethoxyethane, etc.; ester series solvents such asethyl acetate, butyl acetate, etc.; ketone series solvents such asacetone, methyl ethyl ketone, etc.; halogen-containing solvents such asmethylene chloride, chloroform, 1,1,1-trichloroethane, etc.;nitrogen-containing solvents such as dimethylformamide, acetamide,formamide, acetonitrile, etc.; and aprotic polar solvents such asdimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoric triamide,etc., among others. These organic solvents can be used each alone or ina combination of two or more species. The preferred solvents aretoluene, acetone, methylene chloride, tetrahydrofuran,dimethylformamide, acetamide, formamide, acetonitrile, dimethylsulfoxide and N-methylpyrrolidone.

[0101] The reaction temperature in step (3) is −20° C. to 100° C.,preferably 0 to 50° C.

[0102] After completion of the reaction in step (3), the product can berecovered from the reaction mixture by the routine after-treatment. Atypical after-treatment comprises adding water to the reaction mixtureupon completion of the reaction, carrying out an extraction using thecommon extraction solvent, such as ethyl acetate, diethyl ether,methylene chloride, toluene or hexane, and removing the reaction solventand extraction solvent from the extract by, for example, distillation byheating under reduced pressure to provide the objective product. Analternative after-treatment comprises distilling off the reactionsolvent by heating under reduced pressure immediately following thereaction and, then, carrying out the same procedure as above. Theobjective product thus obtained is substantially pure but may be furtherpurified by the conventional procedure such as recrystallization,fractional distillation or chromatography.

[0103] In the compound thus obtained in step (3), i.e. ahalomethyldioxanylacetic acid derivative of the following generalformula (VI):

[0104] wherein R⁴ and R⁵ may each independently be a hydrogen atom, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, thus includingmethyl, ethyl, tert-butyl, hexyl, phenyl, benzyl and p-methoxybenzyl,among others. Of these, methyl is preferred.

[0105] R⁴ and R⁵ may be conjoined each other to form a ring, forexample, R⁴ and R⁵ may form a cyclopentane ring, a cyclohexane ring, acycloheptane ring or a benzocyclopentane ring therebetween to constitutea spiro system with the 1,3-dioxane ring.

[0106] Step (4)

[0107] In this step, the compound obtained in step (3), namely(4R,6S)-configured halomethyldioxanylacetic acid derivative of thefollowing general formula (VI):

[0108] , is reacted with an acyloxylating agent to provide a(4R,6S)-configured acyloxymethyldioxanylacetic acid derivative of thefollowing general formula (VII):

[0109] In the above formula, R³ may for example be a hydrogen atom, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, thus specificallyincluding hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl,tert-butyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl, andp-nitrobenzyl, among others. Of these groups, methyl is the mostpreferred.

[0110] As the acyloxylating agent for use in this step (4), there can bementioned carboxylic acid quaternary ammonium salts of the followinggeneral formula (XI):

[0111] Here, R¹¹, R¹², R¹³ and R¹⁴ each independently represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, thus includingmethyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, n-octyl, phenyl,naphthyl, p-methoxyphenyl and p-nitrobenzyl, among others. Among these,n-butyl is preferred.

[0112] The amount of use of the carboxylic acid quaternary ammonium saltis 1 to 5 molar equivalents, preferably 1 to 3 molar equivalents,relative to the halomethyldioxanylacetic acid derivative.

[0113] Aside from said carboxylic acid quaternary ammonium salt, amixture of a quaternary ammonium salt of the following general formula(XII);

[0114] and a carboxylic acid salt of the following general formula(XIII);

[0115] for instance, can be used likewise as the acyloxylating agent instep (4).

[0116] The acyloxylation reaction using the above mixture of aquaternary ammonium salt and a carboxylic acid salt represents a routeof synthesis which does n ot require said expensive carboxylic acidquaternary ammonium salt but involves only the use of a less expensivequaternary ammonium salt in a smaller amount and is a novel reactiontechnology developed by the inventors of the present invention.

[0117] In the above quaternary ammonium salt, R¹⁵, R¹⁶, R¹⁷ and R¹⁸ mayeach independently be an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, thus including methyl, ethyl, n-propyl, i-propyl, n-butyl,tert-butyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl andp-nitrobenzyl, among others. Preferred is n-butyl.

[0118] X⁵ may for example be a halogen atom, a hydroxyl group or anacyloxy group. Specifically, chlorine, bromine, iodine, hydroxy,acetoxy, butyloxy, benzyloxy, trifluoroacetoxy, etc. can be mentionedand, among them, chlorine, bromine, hydroxy and acetoxy are preferred.Of these, chlorine or bromine is still more preferred.

[0119] The amount of use of said quaternary ammonium salt is 0.05 to 2molar equivalents, preferably not more than a catalytic amount orspecifically 0.1 to 0.9 molar equivalent, relative to thehalomethyldioxanylacetic acid derivative.

[0120] In the above carboxylic acid salt, R³ may for example be ahydrogen atom, an alkyl group of 1 to 12 carbon atoms, an aryl group of6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbon atoms, thusincluding hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl,tert-butyl, n-octyl, phenyl, naphthyl, p-methoxyphenyl andp-nitrobenzyl, among others. Among these, methyl is preferred.

[0121] M represents an alkali metal or an alkaline earth metal, thusincluding lithium, sodium, potassium, magnesium, calcium and barium,among others. The preferred metals are sodium and potassium.

[0122] The symbol n represents an integer of 1 or 2 depending on thevalence of M.

[0123] The amount of use of said carboxylic acid salt is 1 to 15 molarequivalents, preferably 1 to 5 molar equivalents, relative to thehalomethyldioxanylacetic acid derivative.

[0124] The preferred combinations of X⁵ in the quaternary ammonium saltwith M in the carboxylic acid salt are the combination of chlorine forX⁵ in said quaternary ammonium salt with sodium for M in said carboxylicacid salt and the combination of bromine for X⁵ in said quaternaryammonium salt with potassium for M in said carboxylic acid salt.

[0125] For the reaction in step (4), various organic solvents can beused as the reaction solvent. As such organic solvents, there can bementioned hydrocarbon series solvents such as benzene, toluene,cyclohexane, etc.; etherseries solvents such as diethyl ether,tetrahydrofuran, 1,4-dioxane, methyl t-butyl ether, dimethoxyethane,etc.; ester series solvents such as ethyl acetate, butyl acetate, etc.;halogen-containing solvents such as methylene chloride, chloroform,1,1,1-trichloroethane, etc.; nitrogen-containing solvents such asN,N-dimethylformamide, acetamide, formamide, acetonitrile, etc.; andaprotic polar solvents such as dimethyl sulfoxide, N-methylpyrrolidone,hexamethylphosphoric triamide, etc. Those organic solvents can be usedeach alone or in a combination of two or more species. The preferredsolvents are nitrogen-containing solvents such as N,N-dimethylformamide,acetamide, formamide, acetonitrile, etc.; and aprotic polar solventssuch as dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphorictriamide, etc., with N,N-dimethylformamide being more preferred.

[0126] The reaction temperature in step (4) is 0° C. to 200° C.,preferably 50 to 150° C.

[0127] After completion of the reaction in step (4), the product can berecovered from the reaction mixture by the routine after-treatment. Atypical after-treatment comprises adding water to the reaction mixtureupon completion of the reaction and carrying out an extraction using thecommon extraction solvent, such as ethyl acetate, diethyl ether,methylene chloride, toluene, hexane or heptane, and removing thereaction solvent and extraction solvent from the resulting extract by,for example, distillation by heating under reduced pressure to providethe objective product. An alternative method comprises distilling offthe reaction solvent by heating under reduced pressure immediately aftercompletion of the reaction and, then, carrying out the same procedure asabove. The objective product thus obtained is substantially pure but maybe further purified by the conventional procedure such asrecrystallization, fractional distillation or chromatography.

[0128] Step (5)

[0129] In this step, the compound obtained in step (4), namely a(4R,6S)-configured acyloxymethyldioxanylacetic acid derivative of thefollowing general formula (VII):

[0130] , is subjected to solvolysis in the presence of a base accordingto a known method, for instance, to provide the corresponding(4R,6S)-configured hydroxymethyldioxanylacetic acid derivative of thefollowing general formula (I):

[0131] As the base which can be used for this solvolysis in step (5),there can be mentioned eboth inorganic and organic bases such as sodiumcarbonate, potassium carbonate, sodium hydrogencarbonate, potassiumhydrogencarbonate, sodium hydroxide, potassium hydroxide, calciumhydroxide, lithium hydroxide, barium hydroxide, magnesium hydroxide,sodium acetate, potassium acetate, ammonia, triethylamine, pyridine,piperidine, N,N-dimethylaminopyridine and so forth. The preferred baseis potassium carbonate.

[0132] The amount of use of the base in this reaction is 0.001 to 5equivalents, preferably 0.01 to 1.0 equivalent, relative to theacyloxymethyldioxanylacetic acid derivative.

[0133] The solvolysis reaction in step (5) is carried out in water or aprotic organic solvent, or a mixture of either water or a protic organicsolvent with an aprotic organic solvent. As the protic organic solventmentioned above, there can be mentioned alcohol series solvents such asmethanol, ethanol, butanol, isopropyl alcohol, ethylene glycol,methoxyethanol, etc. and amine series solvents such as diethylamine,pyrrolidine, piperidine and so forth. As the aprotic organic solventmentioned above, there can be mentioned hydrocarbon series solvents suchas benzene, toluene, cyclohexane, etc.; ether series solvents such asdiethyl ether, tetrahydrofuran, 1,4-dioxane, methyl t-butyl ether,dimethoxyethane, etc.; ester series solvents such as ethyl acetate,butyl acetate, etc.; ketone series solvents such as acetone, methylethyl ketone, etc.; halogen-containing solvents such as methylenechloride, chloroform, 1,1,1-trichloroethane, etc.; nitrogen-containingsolvents such as dimethylformamide, acetonitrile, etc.; and aproticpolar solvents such as dimethyl sulfoxide, N-methylpyrrolidone,hexamethylphosphoric triamide and so forth.

[0134] The preferred reaction solvent includes water, methanol andethanol.

[0135] The reaction temperature in step (5) is −20° C. to 100° C.,preferably −10 to 50C.

[0136] After completion of the reaction, the reaction product can berecovered from the reaction mixture by the routine after-treatmentmethod. A typical after-treatment method comprises adding water to thereaction mixture at the end of the reaction, extracting the reactionproduct into the common solvent such as ethyl acetate, diethyl ether,methylene chloride, toluene or hexane and removing the reaction solventand extraction solvent by heating under reduced pressure to therebyisolate the objective compound. An alternative method comprises removingthe reaction solvent, for example by heating under reduced pressure,immediately after completion of the reaction and, then, carrying out thesame procedure as above. The objective compound thus obtained issubstantially pure but may be further purified by the routine proceduresuch as recrystallization, fractional distillation or chromatography.

BEST MODE FOR CARRYING OUT THE INVENTION

[0137] The following examples illustrate the present invention infurther detail but are not intended to define the scope of theinvention.

EXAMPLE 1 Tert-butyl (SS)-6-chloro-5-hydroxy-3-oxohexanoate

[0138] Under argon gas, 3.34 g (33 mmol) of diisopropylamine was addeddropwise to 16.7 g (30 mmol) of n-butylmagnesium chloride intoluene/tetrahydrofuran (weight ratio=1:2.5) (1.8 mol/kg) at 40° C. withconstant stirring to prepare a magnesium chloride diisopropylamidesolution.

[0139] Separately, 1.0 g (6.0 mmol) of ethyl(3S)-4-chloro-3-hydroxybutyrate (Japanese Patent Publication No.1723728)and 1.74 g (15 mmol) of tert-butyl acetate were dissolved in 5.0 mL ofdimethoxyethane and the solution was stirred under argon gas at 0 to 5°C. To this solution was added the above magnesium chloridediisopropylamide solution dropwise over 3 hours, and the mixture wasfurther stirred at 20° C. for 16 hours.

[0140] Using a separate vessel, 7.88 g of concentrated hydrochloricacid, 20 g of water and 20 mL of ethyl acetate were mixed together understirring and the above reaction mixture was poured into this vessel.After standing, the organic layer was separated, washed with saturatedaqueous sodium chloride solution and dried over anhydrous magnesiumsulfate and the solvent was distilled off by heating under reducedpressure.

[0141] The residue was purified by silica gel column chromatography(Merck, Kieselgel 60, hexane:ethyl acetate 80:20) to provide 1.14 g oftert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate (colorless oil) in anyield of 80%.

[0142]¹H-NMR (CDCl₃, 400 MHz/ppm): 1.48 (9H, s), 2.84 (1H, dd), 2.91(1H, dd), 3.05 (1H, bs), 3.41 (2H, s), 3.55-3.64 (2H, m), 4.28-4.36 (1H,m)

[0143] COMPARATIVE EXAMPLE 1

Tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate

[0144] In 5.0 mL of tetrahydrofuran were dissolved 1.0 g (6.0 mmol) ofethyl (3S)-4-chloro-3-hydroxybutyrate and 2.78 g (24 mmol) of tert-butylacetate, followed by stirring under argon gas at 0 to 5° C. To thissolution was added a tetrahydrofuran solution containing 24 mmol oflithium diisopropylamide dropwise over 20 minutes, and the mixture wasfurther stirred at 5 to 20° C. for 16 hours.

[0145] In a separate vessel, 6.31 g of concentrated hydrochloric acid,20 g of water and 20 mL of ethyl acetate were mixed by stirring and theabove reaction mixture was poured in the mixture. After standing, theorganic layer was separated, washed with saturated sodium chloride/H₂Oand dehydrated over anhydrous magnesium sulfate and the solvent was thendistilled off by heating under reduced pressure.

[0146] The residue was purified by silica gel column chromatography(Merck's Kieselgel 60, hexane:ethyl acetate=80:20) to provide 86 mg(colorless oil) of tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate ina yield of 6%.

EXAMPLE 2 Tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate

[0147] In 10.0 mL of tetrahydrofuran were dissolved 3.0 g (18.0 mmol) ofethyl (3S)-4-chloro-3-hydroxybutyrate, 5.22 g (45 mmol) of tert-butylacetate, and 6.86 g (72 mmol) of magnesium chloride, and the solutionwas stirred under argon gas at 0 to 5C. To this solution was added atetrahydrofuran solution containing 90 mmol lithium diisopropylamidedropwise over one hour, and the mixture was further stirred at 25° C.for 3 hours.

[0148] In a separate vessel, 21.7 g of concentrated hydrochloric acid,30 g of water and 30 mL of ethyl acetate were mixed by stirring and theabove reaction mixture was poured in this mixture. After standing, theorganic layer was separated and washed with water twice and the solventwas then distilled off by heating under reduced pressure to provide 5.62g of a red oil containing tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate.

[0149] This oil was analyzed by high performance liquid chromatography(column: Nakalai-Tesque, Cosmoseal 5CN-R (4.6 mm×250 mm),eluent:water/acetonitrile=9/1, flow rate 1.0 mL/min, detection at 210nm, column temperature 40° C.). The reaction yield thus found was 65%.

EXAMPLE 3 Tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate

[0150] Under argon gas, a solution composed of 26.71 g (264 mmol) ofdiisopropylamine and 18.8 g of tetrahydrofuran was added dropwise to 150mL (240 mmol) of a solution of n-butyllithium (1.6 mol/L) in hexane toprepare a lithium diisopropylamide solution.

[0151] In 20 mL of tetrahydrofuran were dissolved 12.5 g (75 mmol) ofethyl (3S)-4-chloro-3-hydroxybutyrate and 17.4 g (150 mmol) oftert-butyl acetate, and the resulting solution was stirred under argongas at 0 to 5° C. To this solution was added 42.9 g (75 mmol) of asolution of tert-butylmagnesium chloride in toluene/tetrahydrofuran(1:2.5 by weight) (1.8 mol/kg) dropwise over 30 minutes, and the wholemixture was further stirred at 5° C. for 30 minutes. Then, the lithiumdiisopropylamine solution prepared above was added dropwise over 3hours, and the resulting mixture was further stirred at 5° C. for 16hours.

[0152] In a separate vessel, 60.38 g of concentrated hydrochloric acid,31.3 g of water and 50 mL of ethyl acetate were mixed by stirring, andthe above reaction mixture was poured in this mixture. After standing,the organic layer was separated and washed twice with water and thesolvent was distilled off by heating under reduced pressure to provide22.0 g of a red oil containing tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate.

[0153] As analyzed by the method described in Example 2, the reactionyield was 78%.

EXAMPLE 4 Tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate

[0154] Sakaguchi flasks of 500 mL capacity were respectively chargedwith 50 mL of said medium A and, after sterilization, inoculated withthe microbial strains indicated in Table 1, respectively. Aerobic shakeculture was then carried out at 30° C. for 2 days. From each of theculture broths, the cells were harvested by centrifugation and suspendedin 25 mL of 50 mM phosphate buffer (pH 6.5) containing 1% of tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate (synthesized by the processdescribed in Example 1) and 2% of glucose. The suspension was put in a500 mL Sakaguchi flask and a reaction was conducted under shaking at 30°C. for 20 hours. After completion of the reaction, the reaction mixturewas extracted twice with one volume of ethyl acetate each and the ethylacetate phase was analyzed by high performance liquid chromatography(column: Nakalai-Tesque, Cosmocil 5CN-R (4.6 mm×250 mm), eluent: 1 mMphosphoric acid/H₂O:acetonitrile=5:1, flow rate 0.7 mL/min., detection:at 210 nm, column temperature: 30° C.) for reaction rate and for thediastereomer ratio of the product tert-butyl(3R,5S)-6-chloro-3,5-dihydroxyhexanoate. The results are shown inTable 1. TABLE 1 Reaction Diastereomer ratio Strain of microorganismrate (%) (3R, 5S):(3S, 5S) Hormoascus platypodis IF01471 39 100:0Candida catenulata IF00745 41 100:0 Candida diversa IF01019 33 100:0Candida fructus IF01581 27 100:0 Candida glaebosa IF01353 64 100:0Candida guilliermondii IF00454  9 100:0 Cryptococcus humicola IF00760 20100:0 Candida intermedia IF00761 24  94:6 Candida magnoliae IF0 0705 71100:0 Candida musae IF01582 24 100:0 Candida pintolopesii var. 29 100:0pintolopesii IF00729 Candida pinus IF00741 54 100:0 Candida sake IF0043532 100:0 Candida sonorensis IF010027 23 100:0 Candida tropicalis IF0140128  95:5 Cryptococcus laurentii IF00609 14 100:0 Cryptococcus terreusIF00727 37 100:0 Debaryomyces hansenii var. 16 100:0 fabryi IF00058Geotrichum eriense ATCC22311 24  89:11 Kuraishia capsulata IF00721 12100:0 Kluyveromyces marxianus IF00288  8 100:0 Pichia boyis IF01886 61 95:5 Yamadazyma haplophila IF00947 10 100:0 Pichia membranaefaciensIF00458 27  95:5 Rhodotorula glutinis IF01099 12 100:0 Saccharomycescerevisiae IF00718 16  89:11 Schizoblastsporion kobayasii IF01644 26100:0 Candida claussenii IF00759 24  90:10 Debaryomyces robertsiiIF01277 20 100:0 Zygosaccromyces rouxii IF00493 22  89:11

EXAMPLE 5 Tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate

[0155] A 5-L mini-jar fermenter containing 3 L of medium A wasinoculated with Candida magnoliae IFO0705and incubated at 30° C. with0.5 vvm aeration and stirring at 500 rpm for 24 hours. After completionof cultivation, 30 g of tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate (synthesized by the processdescribed in Example 1) and 60 g of glucose were added and the reactionwas carried out, with the pH maintained at 6.5 with sodium hydroxide,for 18 hours. After completion of the reaction, the cells were removedcentrifugally and the supernatant was extracted twice using 1.5 L ofethyl acetate each. The organic phase was separated and dehydrated overanhydrous sodium sulfate and the solvent was distilled off by heatingunder reduced pressure to recover 24 g of tert-butyl(3R,5S)-6-chloro-3,5-dihydroxyhexanoate as a solid. As analyzed by themethod described in Example 4, the diastereomer ratio of this productwas (3R,5S)/(3S,5S)=100/0.

[0156]¹H-NMR (CDCl₃, 400 MHz/ppm): 1.47 (9H, s), 1.62-1.78 (2H, m), 2.43(2H, d, J=6.4 Hz), 3.51-3.58 (2H, m), 3.75 (1H, bs), 3.84 (1H, bs),4.07-4.13 (1H, m), 4.23-4.28 (1H, m)

EXAMPLE 6 Tert-butyl2-[(4R,6S)-6-(chloromethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate

[0157] In 4.0 mL of acetone was dissolved 1.08 g (4.52 mmol) oftert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate (synthesized by theprocess described in Example 5), followed by the addition of 0.83 mL(6.8 mmol) of 2,2-dimethoxypropane and 8.6 mg (0.045 mmol) ofp-toluenesulfonic acid in the order mentioned. The mixture was thenstirred at room temperature for 4.5 hours, after which the reactionsolvent and the excess 2,2-dimethoxypropane were distilled off byheating under reduced pressure. The residue was diluted with 10 mL ofsaturated sodium hydrogencarbonate/H₂O and extracted 3 times withn-hexane.

[0158] The organic extract was washed with saturated aqueous sodiumchloride solution and dehydrated over anhydrous sodium sulfate and thesolvent was distilled off by heating under reduced pressure to provide1.25 g (colorless oil) of tert-butyl2-[(4R,6S)-6-(chloromethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate in ayield of 99%.

[0159]¹H-NMR (CDCl₃, 400 MHz/ppm): 1.25 (1H, dd), 1.39 (3H, s), 1.45(9H, s), 1.47 (3H, s), 1.77 (1H, dt), 2.33 (1H, dd), 2.46 (1H, dd), 2.40(1H, dd), 2.51 (1H, dd), 4.03-4.10 (1H, m), 4.25-4.30 (1H, m)

EXAMPLE 7 Tert-butyl2-{(4R,6S)-2,2-dimethyl-6-[(methyl-carbonyloxy)methyl]-1,3-dioxan-4-yl}acetate

[0160] In 10 mL of N,N-dimethylformamide were suspended 1.00 g (3.60mmol) of tert-butyl2-[(4R,6S)-6-(chloromethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate(synthesized by the process described in Example 6), 1.16 g (3.60 mmol)of tetra-n-butylammonium bromide and 1.76 g (18.0 mmol) of potassiumacetate, and the suspension was stirred at 100° C. for 20 hours. Aftercooling to room temperature, the reaction mixture was diluted with 20 mLof water and extracted 3 times using n-hexane.

[0161] The organic extract was washed with saturated aqueous sodiumchloride solution and dehydrated over anhydrous sodium sulfate and thesolvent was distilled off by heating under reduced pressure. The residuewas purified by silica gel column chromatography (Merck's Kieselgel 60,hexane:ethyl acetate=80:20) to provide 0.88 g of tert-butyl2-{(4R,6S)-2,2-dimethyl-6-[(methylcarbonyloxy)methyl]-1,3-dioxan-4-yl}acetate(white solid) in a yield of 81%.

[0162]¹H-NMR (CDCl₃, 400 MHz/ppm): 1.27 (1H, dd, J=23.9, 11.7 Hz), 1.39(3H, s), 1.45 (9H, s), 1.47 (3H, s), 1.57 (1H, dm, J=10.3 Hz), 2.08 (3H,s), 2.32 (1H, dd, J=15.1, 5.9 Hz), 2.45 (1H, dd, J=15.1, 6.8 Hz),3.97-4.16 (3H, m), 4.25-4.33 (1H, m)

EXAMPLE 8 Tert-butyl2-{(4R,6S)-2,2-dimethyl-6-[(methyl-carbonyloxy)methyl]-1,3-dioxan-4-yl}acetate

[0163] In 10 mL of N,N-dimethylformamide were suspended 1.00 g (3.60mmol) of tert-butyl2-[(4R,6S)-6-(chloromethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate[synthesized by the process described in Example 6], 0.5 g (1.80 mmol)of tetra-n-butylammonium chloride and 0.89 g (10.8 mmol) of sodiumacetate, and the suspension was stirred at 100° C. for 20 hours. Aftercooling to room temperature, the reaction mixture was diluted with 20 mLof water and extracted 3 times with n-hexane.

[0164] The organic extract was washed with saturated aqueous sodiumchloride solution and dehydrated over anhydrous sodium sulfate and thesolvent was distilled off by heating under reduced pressure. To theresidue was added 8.0 mL of n-hexane again, and the mixture was heatedat 50° C. for dissolution, followed by cooing to −20° C. The crystalswhich separated out were recovered by filtration, washed with coldn-hexane and dried by heating under reduced pressure to provide 0.76 gof tert-butyl2-{((4R,6S)-2,2-dimethyl-6-[(methylcarbonyloxy)-methyl]-1,3-dioxan-4-yl}acetate(white needles) in a yield of 70%.

EXAMPLE 9 Tert-butyl2-[(4R,6S)-6-(hydroxymethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate

[0165] In 100 mL of methanol was dissolved 10 g (33.1 mmol) oftert-butyl2-{((4R,6S)-2,2-dimethyl-6-[(methylcarbonyloxy)-methyl]-1,3-dioxan-4-yl}acetate[synthesized by the process described in Example 8], and underice-cooling and stirring, 0.46 g (3.3 mmol) of potassium carbonate wasadded. The mixture was further stirred under ice-cooling for 4 hours.From this reaction mixture, the reaction solvent was distilled off byheating under reduced pressure, and the residue was diluted with 50 mLof water and neutralized with 0.1 N-hydrochloric acid. This solution wasextracted with ethyl acetate and the resulting organic layer was washedwith water and dehydrated over anhydrous sodium sulfate. The solvent wasthen distilled off by heating under reduced pressure. The oily residuewas decompressed to 1 Torr or less with a vacuum pump to remove thesolvent almost thoroughly. As a result, 8.6 g of tert-butyl2-[(4R,6S)-6,-(hydroxymethyl)-2,2-dimethyl-1,3-dioxan-4-yl]acetate(colorless oil) was obtained in a yield of 100%.

[0166]¹H-NMR (CDCl₃, 400 MHz/ppm): 1.29-1.52 (2H, m), 1.39 (3H, s), 1.45(9H, s), 1.47 (3H, s), 2.05 (1H, bs), 2.33 (1H, dd, J=15.1, 5.9 Hz),2.44 (1H, dd, J=15.1, 6.8 Hz), 3.47-3.53 (1H, m), 3.58-3.64 (1H, m),3.99-4.04 (1H, m), 4.27-4.33 (1H, m)

EXAMPLE 10 Tert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate

[0167] Large-sized test tubes were charged with 7 mL of said medium Band, after sterilization, inoculated with the bacteria shown in Table 2,respectively. Then, aerobic shake culture was carried out at 30° C. for1 day. From the resulting culture broth, the cells were harvested bycentrifugation and suspended in 0.5 mL of 50 mM phosphate buffer (pH6.5) containing 0.5% of tert-butyl(5S)-6-chloro-5-hydroxy-3-oxohexanoate and 1.5% of glucose. Thesuspension was placed in a 10 mL test tube equipped with a stopper andthe reaction was carried out under shaking at 30° C. for 20 hours. Aftercompletion of the reaction, the reaction mixture was extracted with 0.5mL of ethyl acetate and the ethyl acetate phase was analyzed by highperformance liquid chromatography (column: Nakalai-Tesque's Cosmocil5CN-R (4.6 mm×250 mm), eluent: 1 mM phosphoric acid/H₂O:acetonitrile=5:1, flow rate: 0.7 mL/min., detection: at 210 nm, column temperature:30° C.) for reaction rate and for the diastereomer ratio of the producttert-butyl (3R,5S)-6-chloro-3,5-dihydroxyhexanoate. The results areshown in Table 2. TABLE 2 Reaction Diastereomer ratio Strain ofmicroorganism ratio (%) (3R, 5S):(3S, 5S) Brevibacterium stationisIFO12144 37.1 94:6 Corynebacterium ammoniagenes 29.2 92:8 IFO12072Corynebacterium flavescens IFO14136 37.7 94:6 Corynebacterium glutamicum19.6 94:6 ATCC13287 Rhodococcus erythropolis IAM1474 24.8  83:17

EXAMPLE 11 Tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate

[0168] Under argon gas, a solution composed of 2.67 g (26.4 mmol) ofdiisopropylamine and 5 ml of tetrahydrofuran was added dropwise to 15 mL(240 mmol) of a solution of n-butyllithium (1.5 mol/L) in hexane at 5°C. with constant stirring to prepare a lithium diisopropylamidesolution.

[0169] Separately, 240 mg (6 mmol equivalent) of sodium hydride (60% inmineral oil) was washed with hexane and, then, 6 ml of tetrahydrofuranwas added. Then, at 5° C., 1.71 g (18.0 mmol) of magnesium chloride,1.74 g (15.0 mmol) of tert-butyl acetate and 1.0 g (6 mmol) of ethyl(3S)-4-chloro-3-hydroxybutyrate were added and the mixture was stirredfor 30 minutes. To this mixture, the lithium diisopropylamide solutionprepared above was added dropwise over 10 minutes at the sametemperature and the reaction mixture was further stirred at an elevatedtemperature of 25° C. for 3 hours.

[0170] The above reaction mixture was poured in a mixture of 6.47 g ofconcentrated sulfuric acid and 10 ml of water. After the aqueous layerwas separated, the organic layer was washed with 10 ml of water and thesolvent was distilled off by heating under reduced pressure to provide1.78 g of oil. Analysis of this product by the method described inExample 2 revealed that the yield was 64%.

COMPARATIVE EXAMPLE 2 Tert-butyl (5S)-6-chloro-5-hydroxy-3-oxohexanoate

[0171] Omitting the addition of magnesium chloride, the procedure ofExample 11 was otherwise repeated. As analyzed by the method describedin Example 2, the yield was 3%.

INDUSTRIAL APPLICABILITY

[0172] In accordance with the present invention described above, anoptically active 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acidderivative of value as a pharmaceutical intermediate, particularly theintermediate of an HMG-CoA reductase inhibitor, can be produced from aninexpensive, readily available starting material without requiring anyspecial equipment such as low-temperature reaction equipment.

1. A process for producing a compound of the following general formula(I):

wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, R⁴ and R⁵each independently represents hydrogen, an alkylgroup of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbon atoms oran aralkyl group of 7 to 12 carbon atoms, and R⁴ and R⁵ may be conjoinedeach other to form a ring, which comprises (1) reacting an enolateprepared by permitting either a base or a metal having a valency of 0 toact on an acetic ester derivative of the following general formula (II):X²CH₂CO₂R¹  (II)  wherein R¹ represents hydrogen, an alkyl group of 1 to12 carbon atoms, an aryl group of 6 to 12 carbon atoms or an aralkylgroup of 7 to 12 carbon atoms, and X² represents hydrogen or a halogenatom,  with a compound of the following general formula (III):

 wherein R² represents an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and X¹ represents a halogen atom,  at a temperature of not lessthan −30° C. to give a compound of the following general formula (IV):

 wherein R¹ and X¹ are as defined above, (2) reducing this compound withthe aid of a strain of microorganism to give a compound of the followinggeneral formula (V):

 wherein R¹ and X¹ are as defined above, (3) treating this comopund withan acetalizing agent in the presence of an acid catalyst to give acompound of the following general formula (VI):

 wherein R¹ and X¹ are as defined above, R⁴ and R⁵ each independentlyrepresents hydrogen, an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and R⁴ and R⁵ may be conjoined each other to form a ring, (4)acyloxylating this compound with an acyloxylating agent to give acompound of the following general formula (VII):

 wherein R¹, R⁴ and R⁵areas defined above, R³ represents hydrogen, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, and (5) subjectingthis compound to solvolysis in the presence of a base.
 2. The processaccording to claim 1 wherein X² in the acetic ester derivative is ahydrogen atom and the base used for preparation of the enolate is amagnesium amide of the following general formula (VIII):

 wherein R⁶ and R⁷ each represents an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms, an aralkyl group of 7 to12 carbon atoms, or a silyl group, and X³ represents a halogen atom. 3.The process according to claim 2 wherein, in the magnesium amide, R 6and R⁷ are isopropyl groups.
 4. The process according to claim 2 or 3wherein, in the magnesium amide, X³ is a chlorine atom.
 5. The processaccording to claim 1 wherein X² in the acetic ester derivative is ahalogen atom and magnesium or zinc is used as the metal having a valencyof 0 for preparation of the enolate.
 6. The process according to any ofclaims 1 to 5 wherein a polyether is added at the reaction of theenolate.
 7. The process according to claim 6 wherein dimethoxyethane isused as the polyether.
 8. The process according to claim 1 whichcomprises treating a compound of the following general formula (III):

 wherein R² represents an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and X¹ represents a halogen atom,  with a Grignard reagent of thefollowing general formula (IX): X⁴—Mg—R⁸  (IX)  wherein R⁸ represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, and X⁴ represents ahalogen atom, in advance and reacting the resulting compound, at atemperature of not less than −30° C., with an enolate prepared bypermitting either a base or a metal having a valency of 0 to act on anacetic ester derivative of the following general formula (II):X²CH₂CO₂R¹  (II)  wherein R¹ represents hydrogen, an alkyl group of 1 to12 carbon atoms, an aryl group of 6 to 12 carbon atoms or an aralkylgroup of 7 to 12 carbon atoms, and X² represents hydrogen or a halogenatom,  to provide said compound of the following general formula (IV);

 wherein R¹ and X¹ are defined above.
 9. The process according to claim8 wherein, in the Grignard reagent, R⁸ is a tert-butyl group and X⁴ is achlorine atom.
 10. The process according to claim 1 which comprisestreating the compound of the general formula (III) with a base and amagnesium compound in advance and reacting the resulting compound, at atemperature of not less than −30° C., with the enolate prepared bypermitting either a base or a metal having a valency of 0 to act on anacetic ester derivative of the general formula (II) to thereby producethe compound of the general formula (IV).
 11. The process according toclaim 10 wherein the base is sodium hydride, lithium diisopropylamide ormagnesium diisopropylamide.
 12. The process according to claim 10 or 11wherein the magnesium compound is magnesium chloride or magnesiumbromide.
 13. The process according to any of claims 8 to 12 wherein X²in the acetic ester derivative is a hydrogen atom and the base used forpreparation of the enolate is a lithium amide of the following generalformula (X):

 in which R⁹ and R¹⁰ each represents an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms, an aralkyl group of 7 to12 carbon atoms, or a silyl group.
 14. The process according to claim 13wherein R⁹ and R¹⁰ in the lithium amide are isopropyl groups.
 15. Theprocess according to any of claims 1 to 14 which, in the step of thereduction reaction with the aid of a strain of microorganism, uses aculture broth, a cellular fraction thereof or a processed matterthereof, of a strain of microorganism selected from among genera ofmicroorganisms belonging to: Hormoascus, Candida, Cryptococcus,Debaryomyces, Geotrichum, Kuraishia, Hansenulla, Kluyveromyces, Pichia,Yamadazyma, Rhodotorula, Saccharomyces, Schizoblastosporon,Zygosaccharomyces, Brevibacterium, Corynebacterium, and Rhodococcus. 16.The process according to any of claims 1 to 15 which, in the step of thereduction reaction with the aid of a strain of microorganism, uses astrain of microorganism selected from among the genera and species ofmicroorganisms belonging to: Hormoascus platypodis, Candida catenulata,Candida diversa, Candida fructus, Candida glaebosa, Candidaguilliermondii, Cryptococcus humicola, Candida intermedia, Candidamagnoliae, Candida musae, Candida pintolopesii var. pintolopenii,Candida pinus, Candida sake, Candida sonorensis, Candida tropicalis,Cryptococcus laurentii, Cryptococcus terreus, Debaryomyces hansenii var.fabryi, Geotrichumeriense, Kuraishia capsulata, Kluyveromyces marxianus,Pichia bovis, Yamadazyma haplophila, Pichia membranaefaciens,Rhodotorula glutinis, Saccharomyces cerevisiae, Schizoblastosporonkobayasii, Candida claussenii, Debaryomyces robertsii, Zygosaccharomycesrouxii, Brevibacterium stationis, Corynebacterium ammoniagenes,Corynebacterium flavescens, Corynebacterium glutamicum, and Rhodococcuserythropolis.
 17. The process according to any of claims 1 to 16 whereina carboxylic acid quaternary ammonium salt of the following generalformula (XI) is used as the acyloxylating agent:

 wherein R³ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, R¹¹, R¹², R¹³ and R¹⁴ each independently represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms.
 18. The processaccording to claim 17 wherein, in the carboxylic acid quaternaryammonium salt, all of R¹¹ R¹², R¹³ and R¹⁴ are n-butyl groups.
 19. Theprocess according to any of claims 1 to 16 wherein the acyloxylatingagent is a mixture of a quaternary ammonium salt of the followinggeneral formula (XII):

 wherein R¹⁵, R¹⁶, R¹⁷ and R¹⁸ each independently represents an alkylgroup of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbon atoms oran aralkyl group of 7 to 12 carbon atoms, and X⁵ represents a halogenatom, a hydroxyl group or an acyloxy group, and a carboxylic acid saltof the following general formula (XIII):

 wherein R³ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, M represents an alkali metal or an alkaline earth metal,and n represents an integer of 1 or
 2. 20. The process according toclaim 19 wherein, in the quaternary ammonium salt, all of R¹⁵, R¹⁶, R¹⁷and R¹⁸ are n-butyl groups.
 21. The process according to claim 19 or 20wherein, in the quaternary ammonium salt, X⁵ is either chlorine orbromine.
 22. The process according to any of claims 19 to 21 wherein, inthe carboxylic acid salt, M is either sodium or potassium.
 23. Theprocess according to any of claims 19 to 22 wherein the quaternaryammonium salt is used catalytically in an amount of not more than thestoichiometric amount.
 24. The process according to any of claims 1 to23 wherein N,N-dimethylformamide is used as a solvent for acyloxylationreaction.
 25. The process according to any of claims 1 to 24 wherein R¹is a tert-butyl group.
 26. The process according to any of claims 1 to25 wherein R² is an ethyl group.
 27. The process according to any ofclaims 1 to 26 wherein R³ is a methyl group.
 28. The process accordingto any of claims 1 to 27 wherein both of R⁴ and R⁵ are methyl groups.29. The process according to any of claims 1 to 28 wherein X¹ ischlorine.
 30. A process for producing a compound of the followinggeneral formula (IV):

wherein R¹ and X¹ are as defined below, which comprises reacting anenolate prepared by permitting a base or a metal having a valency of 0to act on an acetic ester derivative of the following general formula(II): X²CH₂CO₂R¹  (II)  wherein R¹ represents hydrogen, an alkyl groupof 1 to 12 carbon atoms, an aryl group of 6 to 12 carbon atoms or anaralkyl group of 7 to 12 carbon atoms, and X² represents hydrogen or ahalogen atom, with a compound of the following general formula (III):

 wherein R² represents an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and X¹ represents a halogen atom, at a temperature of not lessthan −30° C.
 31. The process according to claim 30 wherein X² in theacetic ester derivative is a hydrogen atom and the base used forpreparation of the enolate is a magnesium amide of the following generalformula (VIII):

 wherein R⁶ and R⁷ each represents an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms, an aralkyl group of 7 to12 carbon atoms, or a silyl group, and X³ represents a halogen atom. 32.The process according to claim 31 wherein, in the magnesium amide, R⁶and R⁷ are isopropyl groups.
 33. The process according to claim 31 or 32wherein, in the magnesium amide, X³ is a chlorine atom.
 34. The processaccording to claim 30 wherein X² in the acetic ester derivative is ahalogen atom and magnesium or zinc is used as the metal having a valencyof 0 for preparation of the enolate.
 35. The process according to any ofclaims 30 to 34 wherein a polyether is added at the reaction of theenolate.
 36. The process according to claim 35 wherein the polyether isdimethoxyethane.
 37. A process for producing a compound of the followinggeneral formula (IV):

wherein R¹ and X¹ are as defined below, which comprises treating acompound of the following general formula (III):

 wherein R² represents an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and X² represents a halogen atom, with a Grignard reagent of thefollowing general formula (IX): X⁴—Mg—R⁸  (IX)  wherein R⁸ represents analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, and X⁴ represents ahalogen atom, in advance and reacting the resulting compound, at atemperature of not less than −30° C., with an enolate prepared bypermitting a base or a metal having a valency of 0 to act on an aceticester derivative of the following general formula (II): X²CH₂CO₂R¹  (II) wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, and X² represents hydrogen or a halogen atom.
 38. Theprocess according to claim 37 wherein, in the Grignard reagent, R⁸ is atert-butyl group and X⁴ is a chlorine atom.
 39. A process for producingthe compound of the general formula (IV) which comprises treating thecompound of the general formula (III) with a base and a magnesiumcompound in advance and reacting the resulting compound, at atemperature of not less than −30° C., with the enolate prepared bypermitting either a base or a metal having a valency of 0 to act on theacetic ester derivative of the general formula (II).
 40. The processaccording to claim 39 wherein the base is sodium hydride, lithiumdiisopropylamide or magnesium chloride diisopropylamide.
 41. The processaccording to claim 39 or 40 wherein the magnesium compound is magnesiumchloride or magnesium bromide.
 42. The process according to any ofclaims 37 to 41 wherein X² in the acetic ester derivative is a hydrogenatom and the base used for preparation of the enolate is a lithium amideof the following general formula (X):

 in which R⁹ and R¹⁰ each represents an alkyl group of 1 to 12 carbonatoms, an aryl group of 6 to 12 carbon atoms, an aralkyl group of 7 to12 carbon atoms, or a silyl group.
 43. The process according to claim 42wherein, in the lithium amide, R⁹ and R¹⁰ are isopropyl groups.
 44. Theprocess according to any of claims 30 to 43 wherein R¹ is a tert-butylgroup.
 45. The process according to any of claims 30 to 44 wherein R² isan ethyl group.
 46. The process according to any of claims 30 to 45wherein X¹ is chlorine.
 47. A process for producing a compound of thefollowing general formula (V):

wherein R¹ and X¹ are as defined below, which comprises subjecting acompound of the following general formula (IV):

 wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, and X¹ represents a halogen atom, to reduction reactionwith the aid of a strain of microorganism.
 48. The process according toclaim 47 which, in the step of the reduction reaction with the aid of astrain of microorganism, uses a culture broth, a cellular fractionthereof, or a processed matter derived therefrom, of a strain ofmicroorganism selected from among genera of microorganisms belonging to:Hormoascus, Candida, Cryptococcus, Debaryomyces, Geotrichum, Kuraishia,Hansenulla, Kluyveromyces, Pichia, Yamadazyma, Rhodotorula,Saccharomyces, Schizoblastosporon, Zygosaccharomyces, Brevibacterium,Corynebacterium, and Rhodococcus.
 49. The process according to claim 47or 48 which, in the step of the reduction reaction with the aid of astrain of microorganism, uses a strain of microorganism selected fromamong genera and species of microorganisms belonging to: Hormoascusplatypodis, Candida catenulata, Candida diversa, Candida fructus,Candida glaebosa, Candida auilliermondii, Cryptococcus humicola, Candidaintermedia, Candida magnoliae, Candida musae, Candida pintolopesii var.pintolopenii, Candida pinus, Candida sake, Candida sonorensis, Candidatropicalis, Cryptococcus laurentii, Cryptococcus terreus, Debaryomyceshansenii var. fabryi, Geotrichum eriense, Kuraishia capsulata,Kluyveromyces marxianus, Pichia bovis, Yamadazyma haplophila, Pichiamembranaefaciens, Rhodotorula glutinis, Saccharomyces cerevisiae,Schizoblastosporon kobayasii, Candida claussenii, Debaryomycesrobertsii, Zyaosaccharomyces rouxii, Brevibacterium stationis,Corynebacterium ammoniagenes, Corynebacterium flavescens,Corynebacterium glutamicum, and Rhodococcus erythropolis.
 50. Theprocess according to any of claims 47 to 49 wherein R¹ is a tert-butylgroup.
 51. The process according to any of claims 47 to 50 wherein X¹ ischlorine.
 52. A process for producing a compound of the followinggeneral formula (VII):

wherein R¹, R⁴ and R⁵ are as defined below, R³represents hydrogen, analkyl group of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbonatoms or an aralkyl group of 7 to 12 carbon atoms, which comprisesreacting a compound of the following general formula (VI):

 wherein R¹ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, X¹ represents a halogen atom, R⁴ and R⁵ each independentlyrepresents hydrogen, an alkyl group of 1 to 12 carbon atoms, an arylgroup of 6 to 12 carbon atoms or an aralkyl group of 7 to 12 carbonatoms, and R¹ and R⁵ may be conjoined each other to form a ring, with,as an acyloxylating agent, a mixture of a quaternary ammonium salt ofthe following general formula (XII):

 wherein R¹⁵, R¹⁶, R¹⁷ and R⁸ each independently represents an alkylgroup of 1 to 12 carbon atoms, an aryl group of 6 to 12 carbon atoms oran aralkyl group of 7 to 12 carbon atoms, and X⁵ represents a halogenatom, a hydroxyl group or an acyloxy group, and a carboxylic acid saltof the following general formula (XIII):

 wherein R³ represents hydrogen, an alkyl group of 1 to 12 carbon atoms,an aryl group of 6 to 12 carbon atoms or an aralkyl group of 7 to 12carbon atoms, M represents an alkali metal or an alkaline earth metal,and n represents an integer of 1 or
 2. 53. The process according toclaim 52 wherein, in the quaternary ammonium salt, all of R¹⁵, R¹⁶, R¹⁷and R¹⁸ are n-butyl groups.
 54. The process according to claim 52 or 53wherein, in the quaternary ammonium salt, X⁵ is either chlorine orbromine.
 55. The process according to any of claims 52 to 54 wherein, inthe carboxylic acid salt, M is either sodium or potassium.
 56. Theprocess according to any of claims 52 to 55 wherein the quaternaryammonium salt is used catalytically in an amount of not more than thestoichiometric amount.
 57. The process according to any of claims 52 to56 wherein N,N-dimethylformamide is used as the solvent foracyloxylation reaction.
 58. The process according to any of claims 52 to57 wherein R¹ is a tert-butyl group.
 59. The process according to any ofclaims 52 to 58 wherein R³ is a methyl group.
 60. The process accordingto any of claims 52 to 59 wherein both of R⁴ and R⁵ are methyl groups.61. The process according to any of claims 52 to 60 wherein X¹ ischlorine.